Tiny flippers leave tiny tracks on the shore. Palm-sized hatchlings of sea turtles, just out of their egg chamber under the sand, are almost instantly drawn to the sea. After a first wash by a mild wave, they wipe the sand off their eyes with their flippers, and plod towards water. With each flipper-step leaving an imprint on the shore, the shore too is being mapped by the hatchlings. A decade or two later, the females among them may heave themselves up the same beach as gravid mothers.
![A juvenile green sea turtle amid pelagic Sargassum. [Photo by Florida Fish and Wildlife Conservation Commission's Fish and Wildlife Research Institute (CC BY-NC-ND 2.0)]](https://www.wildlifeconservationtrust.org/wp-content/uploads/2021/10/102521-a-juvenile-green-sea-turtle-Chelonia-mydas.jpg)
A juvenile green sea turtle amid pelagic Sargassum. [Photo by Florida Fish and Wildlife Conservation Commission’s Fish and Wildlife Research Institute (CC BY-NC-ND 2.0)]
We have a name for this phenomenon: natal homing. But how are they able to return to the same beach from their foraging grounds thousands of kilometres away? And do they always return to the same beach? We don’t yet have conclusive answers. The one theory on which evidence continues to grow is that they can detect both the angle and the intensity of the earth’s magnetic field. Each beach may have its own magnetic signature, which the turtles ‘remember’ to return to it. But latest research suggests that they might not always return to the exact beach on which they were born, and instead choose a beach with a similar geomagnetic signature, even far away from their natal beach. Another theory is that the hatchings imprint not just the magnetic signature of the beach, but also other unique characteristics like smell, low-frequency sound, seasonal offshore currents, and even celestial cues.
Sea turtles have been elusive to science. Hatchlings disappear into the ocean, and become its spirit, returning only to procreate. That gap, which could be nine to twenty years depending on the species (even species-specific estimates vary greatly), as different species reach sexual maturity at different ages, is often referred to as ‘the lost years’. A recent study, which involved the first long-term offshore tracking of green sea turtles in western North Atlantic waters, using solar-powered satellite tags, has found that hatchlings from beaches along the coast of Florida navigate towards the Sargasso Sea to spend their early years.
The Sargasso Sea is a vast patch of the Atlantic Ocean, located entirely within it, and is the only sea without a land boundary. Named after Sargassum, a genus of brown seaweed that floats en masse on its surface, the Sargasso Sea provides essential habitat to shrimp, crab, fish, and other marine species that have adapted to this floating algae. It is a spawning site for endangered eel species, and part of the annual migratory route of Humpback whales. While theories and anecdotal evidence have been suggesting that young turtles use Sargassum as cover from predators, this is the first study that uses satellite tracking to confirm that green sea turtles go there.
![A juvenile hawksbill sea turtle amid pelagic Sargassum. [Photo by Florida Fish and Wildlife Conservation Commission's Fish and Wildlife Research Institute (CC BY-NC-ND 2.0)]](https://www.wildlifeconservationtrust.org/wp-content/uploads/2021/10/102521-juvenile-hawksbill-sea-turtle.jpg)
A juvenile hawksbill sea turtle amid pelagic Sargassum. [Photo by Florida Fish and Wildlife Conservation Commission’s Fish and Wildlife Research Institute (CC BY-NC-ND 2.0)]
It is estimated that only one in 1,000 to 10,000 sea turtle hatchlings survive to adulthood. Further studies that track them through their lives are essential to conserve them in all their habitats. “If we don’t know where they are and what parts of the ocean are important to them, we are doing conservation blindfolded,” Jeanette Wyneken, a biologist at the Florida Atlantic University and co-author of the research, said in an official statement. Many such open ocean habitats could be under threat from human activity, and may require inter-governmental alliances for protection.
In March 2014, five countries – Bermuda, the U.S., the Azores, Monaco, and the U.K. – signed an agreement committing to protect the Sargasso Sea. The health and long-term viability of this ecosystem is threatened by fishing and shipping traffic, fishing itself, wastewater discharge from ships, harvesting of Sargassum algae for fertilizer and biofuel production, and seabed mining, in addition to the broader effects of climate change.
Celebrated marine biologist Sylvia Earle calls the Sargasso a floating, golden rainforest of the ocean. A terrestrial ecosystem harbouring such rich diversity of threatened wildlife would have received conservation attention much earlier. Out of our sight, other biodiversity hotspots in the open ocean may be on the verge of falling apart. But turtles can take us to those places, and inspire us to protect them.
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About the author: Rizwan Mithawala is a Conservation Writer with the Wildlife Conservation Trust and a Fellow of the International League of Conservation Writers. He has previously worked as an environment journalist with a national newspaper.
Disclaimer: The author is associated with Wildlife Conservation Trust. The views and opinions expressed in the article are his own and do not necessarily reflect the views and opinions of Wildlife Conservation Trust.
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